jenpax I know you are only 60, so elder abuse seems not for you. But however you look at it, call it what you will, you - and your DH - are the victims of domestic abuse and that is a crime. It is a threat that you can use if you need to. next time your daughter starts shouting at you, do not say a word, just turn round and walk out of the room - and keep doing it until she gets the message.
As a start, i think you need to mentally accept that the children are your daughter's and it is her responsibility to look after them, not you, and you must step back and become a grandma and not a parent replacement. Next time she wants to go off to the gym or retreat to her room, tell her that you have to go out, with your DH and she will have to look after the children herself - and walk out of the house. In the meanwhile look for alternative accommodation.
Your daughter is a bully and recognises all the buttons she can press on you to get the response she wants. The childhood your daughters had, sounds perfectly normal to me. Like most parents you had to give them a childhood within your income, but if it included PGL holidays then it was far from impoverished. We were a double income professional family, and our children did have holiday weeks without us, but never PGL, we couldn't afford them.
I know that suggesting counselling is the classic get out clause, but in your case I do think it would really help you tobe able to talk to someone who can help you reset yourself, so that you do not see yourself as a failure of a mother who needs to make -up to her daughter for those failings.
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